From d911c0e9fcf070688691bc65e32e7290c053ca45 Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Thu, 27 Aug 2020 15:01:10 -0700 Subject: [PATCH] mm/error_inject: Fix allow_error_inject function signatures. [ Upstream commit 76cd61739fd107a7f7ec4c24a045e98d8ee150f0 ] 'static' and 'static noinline' function attributes make no guarantees that gcc/clang won't optimize them. The compiler may decide to inline 'static' function and in such case ALLOW_ERROR_INJECT becomes meaningless. The compiler could have inlined __add_to_page_cache_locked() in one callsite and didn't inline in another. In such case injecting errors into it would cause unpredictable behavior. It's worse with 'static noinline' which won't be inlined, but it still can be optimized. Like the compiler may decide to remove one argument or constant propagate the value depending on the callsite. To avoid such issues make sure that these functions are global noinline. Fixes: af3b854492f3 ("mm/page_alloc.c: allow error injection") Fixes: cfcbfb1382db ("mm/filemap.c: enable error injection at add_to_page_cache()") Signed-off-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann Reviewed-by: Josef Bacik Link: https://lore.kernel.org/bpf/20200827220114.69225-2-alexei.starovoitov@gmail.com Signed-off-by: Sasha Levin --- mm/filemap.c | 8 ++++---- mm/page_alloc.c | 2 +- 2 files changed, 5 insertions(+), 5 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index 51b2cb5aa503..db542b494883 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -847,10 +847,10 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask) } EXPORT_SYMBOL_GPL(replace_page_cache_page); -static int __add_to_page_cache_locked(struct page *page, - struct address_space *mapping, - pgoff_t offset, gfp_t gfp_mask, - void **shadowp) +noinline int __add_to_page_cache_locked(struct page *page, + struct address_space *mapping, + pgoff_t offset, gfp_t gfp_mask, + void **shadowp) { XA_STATE(xas, &mapping->i_pages, offset); int huge = PageHuge(page); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index aff0bb4629bd..2640f6741004 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3385,7 +3385,7 @@ static inline bool __should_fail_alloc_page(gfp_t gfp_mask, unsigned int order) #endif /* CONFIG_FAIL_PAGE_ALLOC */ -static noinline bool should_fail_alloc_page(gfp_t gfp_mask, unsigned int order) +noinline bool should_fail_alloc_page(gfp_t gfp_mask, unsigned int order) { return __should_fail_alloc_page(gfp_mask, order); }